Abstract

Do you know someone who has an autoimmune disease? Autoimmune diseases are fairly common, affecting more than 23.5 million people in the United States, which is about 1 in 13 people! You may have heard of some of them, such as diabetes (type 1), rheumatoid arthritis, and celiac disease. Many autoimmune diseases are poorly understood, but they all have one thing in common: they happen because a person's immune system (which normally fights off germs to keep the person healthy) attacks the person's own body by accident. In this science project, you will use M&M's® candies and a die to make a model of the immune system in the human body and find out how a person's genetics affect whether they get an autoimmune disease or not.

Objective

Use a model to investigate how a person's genetics affect their chances of getting an autoimmune disease.

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Credits

Teisha Rowland, PhD, Science Buddies

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APA Style

Science Buddies Staff.
(2018, March 24).
What are the Odds? Modeling the Chances of Getting an Autoimmune Disease.
Retrieved from
https://www.sciencebuddies.org/science-fair-projects/project-ideas/BioMed_p017/medical-biotechnology/modeling-the-chances-of-getting-an-autoimmune-disease

Last edit date: 2018-03-24

Introduction

Autoimmune diseases are fairly common, currently affecting more than 23.5 million people in the United States alone. Some autoimmune diseases include lupus, Graves' disease, Hashimoto's disease, rheumatoid arthritis, type 1 diabetes, and celiac disease. It is thought that there are at least 80 different autoimmune diseases, with new ones being added to the list regularly.

What exactly is an autoimmune disease? To understand that, it is important to first understand what the immune system is. The immune system is made up of different cells and organs in your body, and it normally defends you against germs (like harmful microorganisms). It does this so that you do not get sick, or so that you get well quickly if you do get sick. You are constantly being exposed to microorganisms, which are microscopic organisms. This means they are so small that you usually need a microscope to see one of them. Some microorganisms are more dangerous than others. Any microorganism that can make you sick is called a pathogen. Pathogens include harmful bacteria, microscopic fungi, and viruses. If a pathogen gets into a person's body and makes them sick, then the person is said to be infected by that pathogen, or have an infection. Your immune system is constantly working to defend you against all of these pathogens so that you do not get an infection and get sick.

How does your immune system protect you from pathogens and keep you healthy? The immune system goes through a series of steps called the immune response to fight off any pathogen. Basically, the immune system must recognize the pathogen and then attack and destroy the pathogen. You can watch this video from KidsHealth to see the immune response in action.

Most of the immune response work is carried out by white blood cells, also called leukocytes (pronounced loo-ko-sites). There are several different types of white bloods cells, each with a specific job; you can think of them as soldiers, each with a special skill, that collectively work to defend your body against an invading pathogen. The job of some white blood cells is to find pathogens (or other tiny objects that do not belong in the body). When they are looking for pathogens, it is very important that these white blood cells can tell the difference between the body's own healthy cells and the pathogens. This is referred to as self/non-self recognition. (We will get to why this is so important in a minute.) Once they find a pathogen, these white blood cells then let other cells know that there is a pathogen in the body. When they see the pathogen, B cells—which are a type of white blood cell—make antibodies to fight it. An antibody is a tiny particle that is much smaller than even a cell or most pathogens and it both tags a pathogen as "non-self" and helps to destroy the pathogen. A diagram of antibodies binding onto a pathogen is shown in Figure 1, below. Usually, many antibodies will bind to a single pathogen. Once bound to the pathogen, the antibody often gets help from white blood cells to come and destroy the pathogen.

Figure 1.
During the immune response, antibodies (shown in blue) bind to a pathogen (a bacterium here, shown in red). Once bound to the pathogen, the antibodies often then get help from white blood cells to destroy the pathogen. Note: These are simplified drawings that are not to scale.

So what do autoimmune diseases have to do with the immune system? As mentioned earlier, self/non-self recognition is very important. This is so that the immune system does not accidentally make an antibody that binds to its own healthy human cells. When this happens, it is called autoimmunity or an autoimmune response. Autoimmunity is common and usually not serious. It can also seem somewhat random, probably because the causes are usually not well understood. However, if an autoimmune response is not stopped by the body, it can turn into an autoimmune disease. In an autoimmune disease, the immune system attacks healthy cells in the body (instead of attacking a pathogen). How this happens is different for different autoimmune diseases. For example, in celiac disease, the immune system attacks the intestines after a series of events that starts when antibodies accidentally bind to a part of food that the person is eating (specifically gluten, a protein found in wheat).

As another example, in type 1 diabetes, an autoimmune response destroys the cells that make insulin in a person's body (which can cause the person to have too much sugar in their blood). Before the effects of type 1 diabetes are visible, autoimmune antibodies (antibodies that bind a person's own healthy cells) can be detected. Even if a person has autoimmune antibodies, they are not guaranteed to get type 1 diabetes; however, they do have an increased chance of developing diabetes over their lifetime. The more types of autoimmune antibodies that they have, the greater their risk.

Several factors affect whether a person gets an autoimmune disease. A person's genetics—which are the traits they got from their parents—is one factor. In other words, a person's genetics can make them genetically predisposed, or more likely, to get an autoimmune disease than someone with different genetics. A person with genetics that makes them more likely to get an autoimmune disease is said to have an increased risk or higher risk of getting an autoimmune disease. In other words, they are more likely to get, or have a higher probability of getting, an autoimmune disease than the average person. Another factor that can affect whether a person gets an autoimmune disease is their environment, which includes where they live, what they eat, and things they are exposed to.

Even though autoimmune diseases are common, the immune system actually has several checkpoints to stop an autoimmune response so that it does not turn into an autoimmune disease. Three main checkpoints are listed below. Note that these are simplified versions of what the immune system actually does.

Checkpoint 1: Sometimes white blood cells (specifically B cells, which are made in the bone marrow, or T cells, which are made in the thymus) are made that have autoimmunity, meaning their antibodies bind human cells. The body must destroy them before they escape from the bone marrow or thymus, or they can cause an autoimmune disease.

Checkpoint 2: Right before an immune response is triggered to fight an infection, certain white blood cells (called regulatory T cells) make sure that other white blood cells are not accidentally attacking the body's own cells. They have to do their job correctly to prevent an autoimmune disease from happening.

Checkpoint 3: After a pathogen is destroyed in the body, white blood cells (specifically, activated T cells and B cells) must destroy themselves (through a process called apoptosis, pronounced a-pop-toh-sis) to stop the immune response, or it could lead to an autoimmune disease.

Autoimmune diseases are often treated by suppressing, or stopping, the immune system, but this can have a lot of undesirable side effects. By better understanding the immune response, scientists and doctors can make better treatments for autoimmune diseases.

In this science project, you will use M&M's candies and a six-sided die to make a model of the immune system (using the three checkpoints listed above) to find out how a person's genetics and other environmental factors affect whether they get an autoimmune disease or not. A model is something that engineers and scientists build to represent an object or process in nature, which makes it easier to study. It is usually a simplified version of that object or process. For example, sometimes engineers build small model bridges that are easy to hold and examine so they can study it before they build the real bridge. In your model, you will compare people who have a higher risk of getting an autoimmune disease to people who do not have this higher risk. To model the occurrence of an autoimmune response, you will pick M&M's candies from a bowl and look for matches between their colors. Whether or not an autoimmune response develops into an autoimmune disease is affected by somebody's genetic predispositions, making some people's bodies less likely to stop an autoimmune response. In your model, you will roll a die (representing a random event) to check if an autoimmune response turns into an autoimmune disease. Will you find that if someone is at a higher risk of getting an autoimmune disease, they will definitely get an autoimmune disease? If someone is less likely to get an autoimmune disease, based on their genetics, could they still get an autoimmune disease? Break open a package of M&M's candies and grab a die to find out!

Terms and Concepts

Immune system

Microorganism

Pathogen

Infection

Immune response

White blood cell or leukocyte

Self/non-self recognition

B cells

Antibody

Autoimmunity or autoimmune response

Random

Autoimmune disease

Genetics

Genetically predisposed

Increased risk or higher risk

Probability

Environment

T cells

Model

Questions

In the immune response, what do antibodies do?

What happens in the body that can lead to an autoimmune disease?

What factors can affect whether someone gets an autoimmune disease?

What are three big checkpoints that the immune system has in order to prevent an autoimmune disease?

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Materials and Equipment

M&M's (at least one of each color). One small, 1.69 oz. package of regular M&M's should be sufficient. Alternatively, other small objects that come in six different colors or shapes could be used, such as plastic pattern blocks, which are available from
Amazon.com.

Bowl or cup

Six-sided die

Lab notebook

Figure 2. You will need some M&M's candies, a bowl (or cup), a six-sided die, and your lab notebook to do this science project.

Remember Your Display Board Supplies

Poster Making Kit

ArtSkills Trifold with Header

Poster Lights

What are the Odds? Modeling the Chances of Getting an Autoimmune Disease

Experimental Procedure

Testing the Immune Response Model

In this part of the science project, you will test a model of the immune response—including three checkpoints that are meant to prevent autoimmune diseases—to see how often different people might get an autoimmune disease. You will test the model with people who have different genetic predispositions to getting an autoimmune disease. Since you are using a model, you will not actually test real people, but instead will use M&M's candies selection to represent the random processes of an autoimmune response happening in people. You will roll a die to represent checking each checkpoint's effectiveness at preventing an autoimmune response from turning into an autoimmune disease. You will model different genetic predispositions in people and study how this affects their chances of getting an autoimmune disease.

In your lab notebook, create four data tables like Table 1.

Each data table will represent a group of 20 people with a different genetic predisposition that gives them a different increased risk of getting an autoimmune disease.

In each data table, make enough columns so that you can list the 20 people.

Label each data table one of the following: "Higher Risk at One Checkpoint Group," "Higher Risk at Two Checkpoints Group," "Higher Risk at All Three Checkpoints Group," and "Normal Chances of Autoimmunity Group."

Step in the Model

Person 1

Person 2

Person 3

Etc.

Person 20

Setup

What color was picked?

Checkpoint 1

Color match? (Yes/No)

If yes, what was the die number? (1 to 6)

Checkpoint 2

Color match? (Yes/No)

If yes, what was the die number? (1 to 6)

Checkpoint 3

Color match? (Yes/No)

If yes, what was the die number? (1 to 6)

Did the person get an autoimmune disease? (Yes/No)

Table 1. In your lab notebook, make four data tables like this. Each data table will represent a group of 20 people with a different genetic predisposition to autoimmune diseases.

For the "Higher Risk at One Checkpoint Group" and "Higher Risk at Two Checkpoints Group" data tables, pick any of the three checkpoints to represent people at higher risk.

For the "Higher Risk at One Checkpoint Group" data table, pick any one of the three checkpoints.

Circle or highlight that checkpoint on the data table, or make a note of it in your lab notebook.

For the "Higher Risk at Two Checkpoints Group" data table, pick any two of the three checkpoints.

Again, circle or highlight the checkpoints on the data table, or make a note of them.

Open the package of M&M's. In a bowl, place three M&M's candies of each color (red, green, yellow, brown, blue, and orange).

If your package does not have at least three of each color, you could use fewer M&M's candies, as long as there is an equal number of each of the six colors.

Have the data table you titled "Normal Chances of Autoimmunity Group" ready. You will fill this one out in the next step.

Follow the directions in Figure 3—the "Autoimmunity Model" flowchart—. Use the explanations in steps a–f of this step to help guide you through the process, particularly step 5.d. for when you have a color match and then need to roll a die.

Whenever you randomly pick a candy, look away from the bowl and mix the candies a little so you do not know which color you will pick. No peeking!

In the "Setup" row, write the color of the candy you picked in your data table.

Be sure to write your results in the data table as you do your testing.

If you do not have to roll a die when testing the checkpoints, skip the "If yes, what was the die number?" row for that person.

If you pick matching colors and roll a die when testing the checkpoints, testing should end for the person only if a 6 is rolled on the die. This means the person got an autoimmune disease.

Be sure to read the blue "What it represents" boxes so you know what you are modeling.

At the beginning of the "Setup" and each checkpoint, make sure that all candy has been returned to the bowl and there is still an equal number of each color.

Figure 3. This is a flowchart of the model you will use in this science project. The blue boxes explain what each part of the model represents. As you follow the steps in the model and fill out each data table, keep in mind the blue "What it represents" boxes.

Go through the model for each of the 20 people listed in your data table.

For each person, make sure to fill out the bottom row, "Did the person get an autoimmune disease?"

Once you have done steps 5 and 6 for the first data table, repeat steps 5 and 6 for your other three data tables, with the following small change to represent the higher risk factor of specific checkpoints. When you have picked two matching colors during a checkpoint indicating a person at higher risk (the ones you circled or highlighted in step 2), use the following directions to determine if an autoimmune disease develops instead of the directions explained in 5.d.:

Testing should end for this person if a 2, 3, 4, 5, or 6 is rolled on the die (but not if a 1 is rolled). This means the person got an autoimmune disease. How do you think these people having a higher risk at this checkpoint affects whether an autoimmune response turns into an autoimmune disease?

When you are done, you should have tested what represents 20 people in each of the four data tables, for a total of 80 people represented.

Analyzing Your Results

In this part of the science project, you will analyze your data and determine how genetic predisposition can affect a person's chances of getting an autoimmune disease.

In your lab notebook, make a data table like Table 2.

Normal Chances of Autoimmunity Group

Higher Risk at One of the Checkpoints Group

Higher Risk at Two of the Checkpoints Group

Higher Risk at All Three of the Checkpoints Group

Percentage of People Who Got an Autoimmune Disease

Table 2. Make a data table like this one in your lab notebook. It will be used to summarize your results.

For each of the four data tables you filled out in the "Testing the Immune Response Model," calculate the percentage of people who got an autoimmune disease.

To do this for one of the data tables, first count the number of times you wrote "Yes" in the bottom row ("Did the person get an autoimmune disease?"). Then divide that number by 20 and multiply by 100 to get the percentage of people who got an autoimmune disease.

For example, if in a data table 3 people got an autoimmune disease out of the 20 tested, the percentage of people who got an autoimmune disease would be 3 divided by 20, which is 0.15 or 15%.

Write your answers in the data table in your lab notebook that is like Table 2.

Make a bar graph of the data table you made that is like Table 2.

You can make a graph by hand or use a website like
Create a Graph to make a graph on the computer and print it.

Put the percentage of people who got an autoimmune disease on the y-axis (the vertical axis going up and down). Put the four different risk groups ("Normal Chances of Autoimmunity Group," "Higher Risk at One of the Checkpoints Group," etc.) on the x-axis (the horizontal axis going across). Make a bar for each risk group.

Look at your data tables and graph and try to draw conclusions from your results.

Were there people with at least one higher risk checkpoint who did not get an autoimmune disease? What about people at higher risk at all three checkpoints who did not get an autoimmune disease?

What does this tell you about someone in real life who has an increased risk of getting an autoimmune disease? Is there a chance they will not get the disease?

Similarly, were there people with no higher risk checkpoints who still got an autoimmune disease?

What does this tell you about people's risks in real life?

Note: In your model, the people in the "Normal Chances of Autoimmunity Group" are still genetically predisposed to getting an autoimmune disease, but they have a much lower risk compared to the other groups you investigated. Technically, for most—if not all—autoimmune diseases, it is thought you cannot get the disease unless you have a genetic predisposition.

Did a group of people with more higher-risk checkpoints always have a higher percentage of people who got an autoimmune disease compared to a group with fewer higher risk checkpoints?

Tip: Compare groups that were different by only one checkpoint, such as having one higher risk checkpoint versus two checkpoints, two checkpoints versus three checkpoints, or no higher risk checkpoints versus one.

Were there many times when the color of the M&M's candy matched the "Setup" color (representing an autoimmune response), but the roll of the die did not result in the person getting an autoimmune disease?

If the colors matched, but the die roll did not result in an autoimmune disease, the person had an autoimmunity event that did not turn into a full autoimmune disease. What do you think this tells you about the occurrence of autoimmunity and autoimmune diseases in real people?

Overall, what do your results tell you about being genetically predisposed to getting an autoimmune disease, and the likelihood of actually getting an autoimmune disease? Was this what you expected? Can you explain your results after doing the experiment?

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Variations

In this science project, you modeled different parts of the immune response using probability, or the likelihood or chance that a certain event will happen, such as a person having an autoimmune response turn into an autoimmune disease. But what exactly was the probability of something happening at each part of the model you used? For example, the probability of rolling a 1 on a six-sided die would be 1 out of 6, since there are six different numbers on the die. 1 divided by 6 is 0.17, or a 17% chance of rolling a 1. What is the probability of picking a certain colored M&M's candy from a bowl that has six candies total, each a different color? Try to determine the probability of a certain outcome in different parts of your model, specifically when the M&M's candies are picked and when a die is rolled. How does it relate to the "What it Represents in the Model" part of Figure 2? Do the probabilities match the results you got? For help on probability, visit this webpage:

Can you tweak the model used in this science project to model a greater range of genetic predispositions to getting an autoimmune disease? Would using a different kind of die, such as a four-sided die, an eight-sided die, a twenty-sided die, etc. help? Or would picking other numbers on the die to correlate with "higher risk" provide a greater range?

How would the model change if, initially, you used more M&M's of one particular color in your bowl. For example, what if you had just one blue M&M's candy and two of all the other colors? Could you use this to represent people who have more or fewer autoimmune responses? Could this represent different environmental factors?

Pick a specific autoimmune disease and do some research on it. You may want to ask an adult to help you do this. Try to find out what is known about the causes of the autoimmune disease and how often a person gets its. How can you model its causes using your model? Can you change your model so that it is a better model of the specific disease? Tip: One autoimmune disease that is fairly well understood is celiac disease. Note that models are simplified versions of the real thing; they behave like the real thing for the aspect you like to study.

In this science project, you likely saw an autoimmunity event happen (when the M&M's colors matched) that did not lead to an autoimmune disease. How often did this happen? You can go back and analyze your results for the four different groups of people. Figure out how many times an autoimmunity event happened, how many times it turned into an autoimmune disease, and how many times it did not. Do you see a correlation with the different groups based on the number of checkpoints that are at higher risk?

How could you model other aspects of the immune system? Tip: You will probably need to learn more about the immune system first and then try to figure out how best to model different parts of it. You could use die and candies again or other things to represent different processes or probabilities of events happening.

You could try a different Science Buddies project idea that models a different part of the immune system:

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